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United States Patent |
5,068,958
|
Kosmowski
|
December 3, 1991
|
Method and apparatus for changing tools in an automated machine tool
Abstract
An automated tool changer system for a drilling or other type of machine
tool system. A gripper apparatus transports tools held in a tool magazine
to a tool working unit such as a drill spindle. The tool working unit is
supported by an upper support beam above a workpiece-supporting table
mounted for movement in an X-Y plane. The magazine is supported by a
sliding carriage mounted on the upper support beam, and can be moved
upwardly and downwardly to insert and remove tools from the gripper
apparatus. The gripper apparatus is supported by the X-Y table, and can be
raised or lowered relative to the table during the tool changing
operation. The gripper apparatus is provided with two possible grip
pressures, and with a sensor for detecting the presence of the tool end at
a predetermined grip jaw reference point. The sensor permits the tool to
be inserted into the spindle chuck with a predetermined length of tool
extending from the chuck.
Inventors:
|
Kosmowski; Wojciech (San Juan Capistrano, CA)
|
Assignee:
|
Dynamotion Corporation (Santa Ana, CA)
|
Appl. No.:
|
584807 |
Filed:
|
September 18, 1990 |
Current U.S. Class: |
483/1; 483/10; 483/13; 483/53; 700/179 |
Intern'l Class: |
B23Q 003/157 |
Field of Search: |
29/568,26 A
408/1,35
364/474.21
414/730
|
References Cited
U.S. Patent Documents
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3188736 | Jun., 1965 | Brainard et al. | 29/568.
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3288032 | Nov., 1966 | Pankonin et al. | 90/11.
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3554617 | Jan., 1971 | Weaver | 308/3.
|
3973863 | Aug., 1976 | Smith | 408/241.
|
4000954 | Jan., 1977 | Pateel | 408/3.
|
4088417 | May., 1978 | Kosmowski | 408/1.
|
4419807 | Dec., 1983 | Moulin | 29/568.
|
4486928 | Dec., 1984 | Tucker et al. | 29/774.
|
4520551 | Jun., 1985 | Imhof | 29/568.
|
4654954 | Apr., 1987 | Bayes et al. | 29/568.
|
4656727 | Apr., 1987 | Itoh | 29/568.
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4658494 | Apr., 1987 | Ohtani et al. | 29/568.
|
4715108 | Dec., 1987 | Sugiyama et al. | 29/568.
|
4761876 | Aug., 1988 | Kosmowski | 29/568.
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4922603 | May., 1990 | Kosmowski | 29/568.
|
4928381 | May., 1990 | Yaguchi et al. | 408/35.
|
Foreign Patent Documents |
0028735 | May., 1981 | EP.
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0060638 | Sep., 1982 | EP.
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1808705 | Jul., 1969 | DE.
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1477478 | Aug., 1969 | DE.
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1920275 | Feb., 1970 | DE.
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1389246 | Jan., 1965 | FR.
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2382828 | Nov., 1978 | FR.
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0132875 | Nov., 1978 | JP.
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0157413 | Dec., 1980 | JP.
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0082146 | Jul., 1981 | JP.
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5695560 | Aug., 1981 | JP.
| |
0094951 | Jun., 1983 | JP.
| |
168441 | Jul., 1986 | JP | 29/568.
|
289508 | Aug., 1970 | NL.
| |
1077752 | Mar., 1984 | SU.
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1139610 | Feb., 1985 | SU | 29/568.
|
1202361 | Aug., 1970 | GB.
| |
1215917 | Dec., 1970 | GB.
| |
1229161 | Apr., 1971 | GB.
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1234936 | Jun., 1971 | GB.
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1249296 | Oct., 1971 | GB.
| |
1408131 | Oct., 1975 | GB.
| |
2014882 | Sep., 1979 | GB.
| |
2021448 | Dec., 1979 | GB.
| |
Primary Examiner: Briggs; William
Attorney, Agent or Firm: Roberts and Quiogue
Claims
What is claimed is:
1. A method of inserting a first end of an elongated tool of unknown length
into a working unit so that a predetermined length of the tool extends
from the unit, comprising a sequence of the following steps:
(i) gripping the tool in a gripper device with a relatively high gripping
pressure so that the first end of the tool extends from the gripper
device, with a length of the tool received within the gripper device which
is less than the predetermined length;
(ii) aligning the gripper device with the working unit;
(iii) effecting relative movement between the gripper device and the
working unit to insert the first end of the tool into the working unit;
(iv) gripping the tool by the working unit and reducing the gripping
pressure of the gripper device on the tool so that further relative
movement of the gripper and the working unit causes sliding movement of
the tool in the gripper device;
(v) effecting further relative movement between the gripper device and the
working unit to reduce the distance therebetween while causing the tool to
slide further within the gripper device until the length of the tool
received within the gripper device is substantially equal to said
predetermined length;
(vi) releasing the tool gripping by the working unit and increasing the
gripping pressure of the gripper device; and
(vii) effecting further relative movement between the gripper device and
the working unit to bring the gripper device and the working unit
substantially adjacent each other to insert said tool into said working
unit with said predetermined length extending from the working unit.
2. The method of claim 1 further comprising the step (viii) of releasing
said tool by said gripper device and withdrawing the gripper device to
allow the working unit to perform a work task with the inserted tool.
3. The method of claim 1 wherein the gripper device is movable toward the
working unit between a first position away from the working unit and a
second position toward the working unit, and the step (iii) of effecting
relative movement to insert the tool into the working unit comprises
moving the gripper device from the first position to the second position.
4. The method of claim 3 wherein the working unit is movable toward and
away from the gripper device, and said step (v) comprises moving the
working unit toward the gripper device until the tool is inserted into the
gripper device said predetermined distance.
5. The method of claim 4 wherein said step (vii) comprises moving the
working unit further toward the gripper device until substantially
adjacent one another.
6. The method of claim 1 further characterized in that the working unit
comprises a drilling spindle and the tool comprises a drilling tool.
7. The method of claim 1 wherein said gripper device comprises at least two
gripper jaws which may selectively grip said tool with either a relatively
high gripping force or a relatively low gripping force.
8. The method of claim wherein said step (v) comprises sensing the presence
of the tip of said tool at a point spaced from the tip of the gripper
device by a distance equal to said predetermined distance, and stopping
said relative movement when the tip is sensed at this point.
9. Apparatus for inserting a first end of an elongated tool of unknown
length into a working unit so that a predetermined length of the tool
extends from the unit, comprising:
a gripper device for receiving a second end of the tool and selectively
gripping the tool with a relatively high gripping force or a relatively
low gripping force;
means for inserting the second end of the tool in said gripper device so
that the first end of the tool extends from the gripper device, with a
length of the tool received within the gripper device which is less than
the predetermined length;
means for aligning the gripper device with the working unit;
means for effecting relative movement between the gripper device and the
working unit to insert the first end of the tool into the working unit
with said tool being gripped by said relatively high gripping force of
said gripper device;
means for gripping the tool by the working unit and reducing the gripping
pressure of the gripper device so that further relative movement of the
gripper and the working unit causes sliding movement of the tool in the
gripper device;
means for effecting further relative movement between the gripper device
and the working unit to reduce the distance therebetween to cause the tool
to slide within the gripper device until said length of the tool received
within the gripper device is substantially equal to said predetermined
length;
means of releasing the tool gripping of the tool by the working unit and
increasing the gripping pressure of the gripper device; and
means for effecting further relative movement between the gripper device
and the working unit to bring the gripper device and the working unit
substantially adjacent each other to insert said tool into said working
unit with said predetermined length extending from the working unit.
10. The apparatus of claim 9 further comprising means for releasing said
tool by said gripper device and effecting relative movement between the
gripper device and the working unit after the tool has been inserted into
the working unit with a predetermined length extending therefrom, to allow
the working unit to perform a work task with the inserted tool.
11. The apparatus of claim 9 further comprising means for moving the
gripper device between a first position away from the working unit and a
second position toward the working unit to insert the tool into the
working unit.
12. The apparatus of claim further comprising means for moving the working
unit toward the gripper device to insert the tool into the gripper device
said predetermined distance.
13. The apparatus of claim 12 further comprising means for moving the
working unit further toward the gripper device until substantially
adjacent one another.
14. The apparatus of claim 9 further characterized in that the working unit
comprises a drilling spindle and the tool comprises a drilling tool.
15. The apparatus of claim 9 wherein said gripper device comprises at least
two gripper jaws which may selectively grip said tool with either a
relatively high gripping force or a relatively low gripping force.
16. An improved gripper apparatus for an automated tool changer system,
comprising:
a plurality of grip jaws each characterized by a jaw tip;
means for closing said jaws to exert gripping force on a tool inserted
therebetween, said closing means comprising means for selectively applying
a relatively high gripping force and a relatively low gripping force;
means for translating said gripper jaws along a predetermined axis between
a first position and a second position; and
sensor means for sensing the condition that a tool has been inserted into
the grip of the jaws a predetermined distance from the jaw tips.
17. The apparatus of claim 16 wherein said grip jaws each further comprise
a jaw member arranged to pivot about a pivot point, said jaw tip defined
at one end of the jaw member, the jaw member further characterized by a
second end disposed on the other side of said pivot point from the jaw
tip, and said means for closing said jaws comprises means for exerting a
force on said second ends of said respective jaw members to cause said jaw
members to pivot about said pivot point and urge the jaw tips toward one
another.
18. The gripper apparatus of claim 17 further comprising means for opening
said jaws, said opening means comprising means for exerting a force on
said second ends of said respective jaw members to cause said jaw members
to pivot about said pivot point and urge the jaw tips toward one another.
19. The apparatus of claim 18 wherein said opening means and said closing
means further comprises a pneumatic actuator coupled to said second ends
for exerting pulling or pushing forces on said second ends of said jaw
members.
20. The apparatus of claim 19 wherein pneumatic actuator is actuated by
application of fluid under pressure, and said means for exerting a
selective gripping force comprises means for modulating the fluid pressure
applied to said actuator to exert said force on said second ends of said
jaws.
21. The apparatus of claim 19 wherein first pneumatic actuator is
characterized by a first cylinder and a first piston, and said means for
translating said gripper jaws comprises a second pneumatic actuator
characterized by a second cylinder and a piston member, said second
actuator comprising means for translating said second piston member along
an actuator axis, and wherein said first pneumatic actuator and said
gripper jaws are carried by said second piston member of said second
actuator.
22. The apparatus of claim 21 wherein said piston of said second actuator
is hollow and receives said first piston for sliding movement therein, and
wherein said second piston further comprises means for defining said first
cylinder of said first actuator at one end thereof.
23. The apparatus of claim 22 wherein said first piston further comprises
means for defining a region of increased diameter thereof which is fitted
within a first chamber of said first cylinder, and said first actuator
further comprises means for pressurizing said chamber on either a first
side or a second side of said region of increased diameter to thereby urge
said piston to move in one direction or the other along its axis.
24. The apparatus of claim 23 wherein said second piston further comprises
means for defining a second region of increased diameter which is fitted
within a second chamber of said second cylinder, and said second actuator
further comprises means for pressurizing said second chamber of said
second actuator on either a first side or a second side of said second
region of increased diameter to thereby urge said second piston to move in
one direction or the other along its axis.
25. A tool changer system for a machine tool characterized by at least one
spindle driving a replaceable tool having a shank and a tool end, a
workpiece carrier mounted for movement in a plane, the spindle being
translatable to effect movement of the tool relative to the workpiece
carrier, the system comprising:
a tool magazine for releasably holding a plurality of said tools, said
magazine comprising means for effecting translating movement of said
magazine relative to the workpiece carrier;
a gripper apparatus secured to said workpiece carrier and comprising
gripper means for receiving said tools in an inserted position within a
tool gripper and selectively gripping said tools with a selectable grip
pressure of either a relatively high grip pressure or a relatively low
grip pressure to transfer tools between said spindle and said magazine,
and means for effecting translating movement of said gripper means
relative to said workpiece carrier;
means for sensing when the tool has been inserted to a predetermined depth
in said tool gripper and generating an insertion depth signal indicative
of such condition;
controller means for inserting the tool into the spindle so that a
predetermined length of tool extends from the spindle, comprising means
for aligning the gripper apparatus with a selected one of the tools in the
magazine, and causing translation between the gripper and the magazine to
insert the tool into the gripper means so that the length of tool inserted
into the gripper means is less than said predetermined length, gripping
the tool with the relatively high gripping pressure, thereafter aligning
the gripper apparatus with the spindle, translating the gripper means in
relation to the workpiece carrier to insert a portion of the exposed tool
into the spindle, causing the spindle to securely grip the inserted
portion of the tool, reducing the grip pressure of the gripper device,
translating the spindle relative to the gripper device to insert more of
the tool into the gripper until the insertion depth signal is generated,
increasing the gripper device grip pressure and releasing the tool grip by
the spindle; and translating the spindle toward the gripper device until
the spindle is directly adjacent the gripper device so that said
predetermined length of tool extends from the spindle; and releasing the
gripping pressure of the gripper apparatus and causing the spindle to grip
the tool in its inserted position.
Description
BACKGROUND OF THE INVENTION
The present invention relates to high speed automated machines for
performing machine operations on a workpiece, and more particularly to
tool changer systems for such automated machines.
A preferred application to which the invention relates is that of printed
circuit board drilling. Printed circuit boards are in universal use today
to mount and interconnect electrical components forming electrical
circuitry. Typically the leads of the components are inserted through
holes drilled in the boards to form predetermined hole patterns. Various
systems are known in the art for automated drilling of the holes in
printed circuit boards. One such system is described in U.S. Pat. No.
4,761,876. The system described therein is particularly well suited to
drilling very small diameter holes, and describes a tool changer which
employs a plurality of tool magazines and clips to hold the tools with the
tools being secured or released by a top plate which captures the tools in
a shank groove of reduced c ross-sectional dimension. The groove is formed
in either the shank or in a tool collar which is fitted on the shank.
The tool changer system of the '876 patent works well. the use of tools
with the groove formed directly in the shank works particularly well,
since for high speed operation, the tool is well balanced. The use of a
collar can lead to balance problems at very high speeds of operation,
unless care is taken in the fabrication and fitting of the collar to the
drilling tool. However, a disadvantage of the tool changer system of the
'876 patent is the additional cost of either forming the groove in the
shank or providing the collar. For example the cost of machining the
groove on the shank of a drilling tool can add as much as $.50 to the cost
of each tool, while a plastic collar can add $.10 to cost of the tool. A
given drilling system with multiple spindles such as the system described
in the '876 patent which undergoes heavy use can use hundreds of thousands
of drilling tools in a single year of operation. The added cost of
machining the grooves in the tool shanks or fabricating and fitting the
plastic collars to the tool can add tens of thousands of dollars to the
operating cost of a single multiple spindle drilling system. This is so
even if the drills are sharpened and reused several times.
The use of sharpened tools leads to another problem. Whereas new tools have
a given or known nominal length, tools lose some of their length as a
result of being sharpened. It is desirable to have a known length of tool
extending from the drilling spindle during the drilling operation, so that
the length of the drilling stroke does not carry the tool tip too far, or
fail to extend the drill tip completely through the workpiece or as far as
desired. In the past, some systems have relied on the placement of the
collar to register the insertion position of the drill in the spindle. The
use of such collars leads to cost and balance disadvantages as described
above.
It is therefore an object of the present invention to provide a method and
apparatus which can reliably change tools used in an automated machine
tool without requiring the tools to be modified, and which can insert
tools of various lengths in the working unit with a given length of tool
extending therefrom.
SUMMARY OF THE INVENTION
A method and corresponding apparatus is disclosed for inserting a first end
of an elongated tool of unknown length into a working unit so that a
predetermined length of the tool extends from the unit. The method
comprises a sequence of the following steps.
(i) Gripping the tool in a gripper device with a relatively high gripping
pressure so that the first end of the tool extends from the gripper
device, with a length of the tool received within the gripper device which
is less than the predetermined length.
(ii) Aligning the gripper device with the working unit.
(iii) Effecting relative movement between the gripper device and the
working unit to insert the first end of the tool into the working unit.
(iv) Gripping the tool by the working unit and reducing the gripping
pressure of the gripper device on the tool so that further relative
movement of the gripper and the working unit causes sliding movement of
the tool in the gripper device.
(v) Effecting further relative movement between the gripper device and the
working unit to reduce the distance therebetween while causing the tool to
slide further within the gripper device until the length of the tool
received within the gripper device is substantially equal to said
predetermined length.
(vi) Releasing the tool gripping by the working unit and increasing the
gripping pressure of the gripper device.
(vii) Effecting further relative movement between the gripper device and
the working unit to bring the gripper device and the working unit
substantially adjacent each other to insert said tool into said working
unit with said predetermined length extending from the working unit.
In a preferred apparatus, the gripper device comprises a plurality of grip
jaws each characterized by a jaw tip, and means for closing said jaws to
exert gripping force on a tool inserted therebetween. The closing means
comprising means for selectively applying a relatively high gripping force
and a relatively low gripping force.
The gripper device further includes means for translating the gripper jaws
along a predetermined axis between a first position and a second position,
and sensor means for sensing the condition that a tool has been inserted
into the grip of the jaws a predetermined distance from the jaw tips. The
sensor signal is employed in the insertion method.
A preferred application for the invention is as a tool changer system for a
machine tool characterized by at least one spindle driving a replaceable
tool having a shank and a tool end, a workpiece carrier mounted for
movement in a plane, the spindle being translatable to effect movement of
the tool relative to the workpiece carrier. The tool changer system
comprises a tool magazine for releasably holding a plurality of said
tools, the magazine comprising means for effecting translating movement of
said magazine relative to the workpiece carrier.
The system further includes a gripper apparatus secured to the workpiece
carrier and comprising gripper means for receiving said tools in an
inserted position within a tool gripper and selectively gripping said
tools with a selectable grip pressure of either a relatively high grip
pressure or a relatively low grip pressure to transfer tools between the
spindle and the magazine, and means for effecting translating movement of
the gripper means relative to the workpiece carrier. Means are provided
for sensing when the tool has been inserted to a predetermined depth in
the tool gripper and generating an insertion depth signal indicative of
such condition.
The system further includes a controller for inserting the tool into the
spindle so that a predetermined length of tool extends from the spindle.
The controller comprising means for aligning the gripper apparatus with a
selected one of the tools in the magazine, and causing translation between
the gripper and the magazine to insert the tool into the gripper means so
that the length of tool inserted into the gripper means is less than said
predetermined length, gripping the tool with the relatively high gripping
pressure, thereafter aligning the gripper apparatus with the spindle,
translating the gripper means in relation to the workpiece carrier to
insert a portion of the exposed tool into the spindle, causing the spindle
to securely grip the inserted portion of the tool, reducing the grip
pressure of the gripper device, translating the spindle relative to the
gripper device to insert more of the tool into the gripper until the
insertion depth signal is generated, increasing the gripper device grip
pressure and releasing the tool grip by the spindle; and translating the
spindle toward the gripper device until the spindle is directly adjacent
the gripper device so that said predetermined length of tool extends from
the spindle; and releasing the gripping pressure of the gripper apparatus
and causing the spindle to grip the tool in its inserted position.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages of the present invention will
become more apparent from the following detailed description of an
exemplary embodiment thereof, as illustrated in the accompanying drawings,
in which:
FIG. 1 is a front elevation view of an automated drilling machine employing
the tool changer system of the present invention.
FIGS. 2-5 illustrate the tool magazine fixture employed in the tool changer
system.
FIGS. 6-9 illustrate the tool gripper comprising the tool changer system.
FIGS. 10-14 illustrate a tool clip as used in the tool changer system.
FIG. 15 is a simplified block diagram illustrating the controller and its
general connection with elements of the tool changer system.
FIGS. 16-24 illustrate the sequence by which tools are transferred from the
tool magazine clip to the drilling spindle in accordance with the
invention.
FIG. 25 illustrates the capability of the tool changer to handle over-sized
tools.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, a front elevation view is shown of the general
configuration of a high speed drilling system 50 employing a tool changing
system in accordance with the present invention. In general, the drilling
system 50 is as described in U S. Pat. No. 4,761,876, incorporated herein
by this reference, with the exception of the tool changer system. While
the invention is described with respect to drilling systems, it will be
appreciated that the invention may be used advantageously with other types
of automated machines employing a plurality of tools, such as milling and
routing machines, for example.
As described in U.S. Pat. '876, the system 50 is a multiple spindle system,
having four pairs of spindles; one spindle of each pair is adapted for
drilling of medium to large diameter holes in workpieces, and the second
spindle of the pair is adapted for high speed drilling of small diameter
holes. The spindles 85-88 of the former group have pneumatically operated
chucks which are opened and closed to grip a drill bit by air pressure,
while the spindles 81-84 of the latter group have centrifugally operated
chucks which statically grip the tool shanks by friction.
The spindles 81-88 are mounted on a top support beam 80 for translation
upwardly and downwardly in the Z axis directions. A work piece carrier or
supporting table 70 is supported below the top beam 80 for movement in the
X-Y plane. The support for the table 70 and the means for moving the table
in the X-Y plane are described in U.S. Pat. No. 4,761,876.
In accordance with the invention, a plurality of tool gripper apparatus 100
are mounted along the forward edge of the X-Y table 70, one gripper
apparatus 70 for each pair of spindles. A plurality of tool magazines 200,
each for holding a plurality of removable tool clips 250, is mounted
adjacent the respective spindles on the top support beam 80 for
translation in the Z direction. As will be described in more detail below,
the gripper apparatus 100 provides a means to transport a selected tool
from the tool magazines 200 to the corresponding spindle chuck, and vice
versa, i.e., to load and unload the spindles with selected tools.
The magazine assembly 200 is shown in more detail in FIGS. 2-5. The
assembly 200 includes a magazine housing 210 which defines a plurality of
longitudinal magazine slots 212. The slots 212 accept respective tool
clips 250 which hold the individual tools 280. The clips 250 are
releasably locked into the respective slots 212 by a spring-loaded lever
214, with end 215 of the lever urged into contact with the shoulder 252
formed at a corner of the clip 250. Thus, the respective clips can be
loaded into the magazine, and are locked in place by action of the lever
214. To remove a clip 250, the lever tip 216 is pressed down, releasing
the clip and permitting it to be slid out of the slot 212.
The magazine assembly 200 further comprises a means for raising and
lowering the magazine housing 210 along the Z axis. The housing 210 is
mounted on a slide member 220 which is bearing mounted with respect to a
corresponding V-block member 224 secured to the upper support beam 80. The
slide member 220 and V-block member 224 are shown in further detail in
FIGS. 3 and 5, and comprise a commercially available cross roller slide
assembly. A suitable assembly is available from Daedal, Box 500, Harrison
City, Penna. 15636, as the model CR4601.
An air cylinder 230 is mounted to the stationary member 224, with the end
of its piston secured to the movable slide member 220. The cylinder 230 is
a double-acting cylinder, and may be actuated to either extend or retract
the piston 232. In the retracted position, the magazine housing is raised
to its uppermost position relative to the X-Y table 70. In the extended
position the housing is lowered to its lowermost position.
Upper and lower optical sensors 236 and 238 sense the presence of pin 226
which extends from the side of the slide member 220 to provide sensor
indication signals to the controller of the tool changer system (FIG. 15)
that the magazine assembly 200 is at either the upper position or the
lower position. The sensors 236 and 238 employ light sources which direct
a light beam across a slot through which the pin 226 passes in its travel.
A photosensitive detector comprising the sensor detects the interruption
of the light beam when the pin passes through the sensor slot. Thus, in
FIG. 4, element 236A represents the light source, and element 236B
represents the detector. Such sensors are commercially available, and well
known to those skilled in the art.
An exemplary gripper apparatus 100 is illustrated in further detail in
FIGS. 6-9. The apparatus is secured to the forward edge of the X-Y table
70 as generally indicated in FIG. 7 by a support bracket 102. Generally
the gripper apparatus includes a pair of gripper jaws which may be opened
and closed, and a means for raising and lowering the jaws along the Z
axis.
The gripper 100 further comprises a pair of optical sensors 104 and 106
appropriately positioned above and below the bracket 102 to sense the
presence of pin 108 protruding from the side of a rod 107 carried by the
gripper jaw assembly, as shown in FIG. 8. The sensors 104 and 106 operated
in a manner similar to the sensors 236 and 238 described with respect to
the tool magazine apparatus, and to sense the positioning of the gripper
apparatus at its upper and lower positions relative to the X-Y table.
FIG. 8 illustrates the gripper apparatus 100 in longitudinal cross-section.
The outer housing 120 serves as the cylinder for the Z axis pneumatic
cylinder actuator which moves the gripper apparatus upwardly and
downwardly along the Z axis. A hollow cylindrical member 122 serves as the
piston for the Z axis drive actuator. The member 122 further defines a
region 124 of increased cross-sectional diameter.
The cylinder defining housing 120 is provided with sealing structures 126
and 130 at each end thereof and with O-ring seals 128 and 132, to provide
a seal against the pressure of the air (or other fluid) used to pressurize
the cylinder chamber 134. An O-ring seal 138 seals between the edge of the
region 124 and the inner surface of the housing 120. By admitting
pressurized air either through the air line 138 or through air line 140,
force is exerted against the annular region of the piston 122 to either
move the piston 122 upwardly or downwardly.
The piston 122 carries the jaws 110 and 112 and the jaw actuating
mechanism, in this case another double acting pneumatic actuator. The
piston 122 is hollow throughout its length to receive a piston 142 of the
second pneumatic actuator, and one end 122A is further relieved to accept
a region 144 of increased cross-sectional dimension of the piston 142. As
with the Z-axis pneumatic actuator, sealing structures 146, 148 and 150
seal the jaw pneumatic actuator. O-rings 152, 154, 156, 158 also aid in
this sealing function. To operate the second actuator, pressurized air is
admitted either through the air line 160 or the air line 162 to force the
second actuator piston either down or up, by exerting pressure on one side
or the other of the annular region 144. Of course, as is well known to
those skilled in the art, means are provided for releasing the pressure on
the other line which is not pressurized.
The second actuator piston 142 opens and closes the jaws 110 and 112. As
shown in FIG. 8, the respective jaw members 110 and 112 each comprise in
cross-section, a generally L-shaped member. Jaw member 110 is mounted for
pivoting movement about pivot pin 164, whose ends are secured in the
housing 170 (FIG. 6). Jaw member 112 is mounted for pivoting movement
about pivot pin 166, whose ends are also secured in the housing 170.
Extreme ends of the jaw members have dogs 172 and 174 extending therefrom.
A coupling fixture 176 is secured to the end of the second actuator piston
142, and moves upwardly and downwardly with the piston. The fixture 176
has opposed dogs 178 and 180 formed at opposite sides thereof. Respective
chain links 182 and 184 are pivotally attached to respective dogs of the
coupling fixture and the jaw members, via pins 186, 188, 190 and 192. The
links 182 and 184 provide a means of transmitting pivoting force to the
dogs 172 and 174 to open or close the tips of the jaws 110 and 112.
The Z-axis and jaw pneumatic actuators can be operated independently. FIG.
9 shows the jaws in the fully opened position, while the jaws are shown in
the closed position in FIG. 8.
In accordance with the invention, the system 50 further comprises means for
modulating the gripping pressure exerted by the grip jaws. Thus, the air
pressure applied to line 160 can be either a relatively high pressure to
securely grip the tool, or a relatively low pressure to grip the tool with
a relatively low grip pressure. The low pressure is sufficient to hold the
tool in place within the grip jaws against the force of gravity, but
readily allows slippage when the tool is held by a spindle chuck during
the tool insertion sequence described below.
The gripper apparatus 100 further includes an optical sensor for sensing
the presence of the end of the tool at a reference with respect to the jaw
tips. As shown in FIG. 9, the jaws 110 and 112 are formed with respective
semicircular indentations 111 and 113 at the reference line point close to
the pivot points. The optical sensor is similar to the sensors 236 and
238, and comprises a light source 114 which generates a light beam through
the opening defined by the indentations 111 and 113 toward a
photosensitive detector 116 on the other side of the jaws. The optical
detector 116 generates a signal indicative of the interruption of the
light beam once the tool has been inserted in the jaws to the extent of
reference line 117.
FIGS. 10-14 illustrates an exemplary clip 250 in further detail. Each clip
250 includes a plurality of aligned openings 254 into which the shank ends
of the tools 280 are fitted (FIG. 14). The shank receiving end of the
openings 254 are funnel-shaped, while the opposite ends are counter-bored
with an enlarged diameter to define a shoulder 254 which provides a stop
surface for an O-ring 258. A cylindrical insert 260 is fitted into the
counterbore to secure the O-ring 258 in place. A cap plate 262 is fitted
over the counter-bored ends of the openings 254 to provide a stop surface
for the shank ends of the tools 280 (FIG. 14). The O-rings 256 are made of
a resilient material such as neoprene, and have a slightly smaller inner
opening diameter than the smaller diameter of the opening 254 to
frictionally engage the shank of the tool 280. This frictional engagement
holds the tool 280 in the clip 250 until removed by the gripper apparatus
100.
FIG. 15 is a simplified block diagram of the control elements of the tool
changer system for an exemplary spindle pair 81, 85. The controller 300
comprises a digital computer programmed to carry out the various functions
needed to carry out the tool changing functions. Typically the controller
functions will be integrated with the system controller for the drilling
system such as the system control unit 505 described in U.S. Pat. No.
4,761,876. The controller 300 controls the air cylinder 230 through the
control valve 302 to raise or lower the magazine 200. Another control
valve 306 is controlled by the controller 300 to open and close the
pneumatically operated chuck of drilling spindle 85. Other valves 308 and
310 are controlled by the controller 300 to operate the pneumatic
actuators of the gripper apparatus 100 to raise or lower the apparatus and
to open or close the grip jaws. Valve 311 controls the pressure supplied
to the gripper jaws via valve 310, to provide line pressure or low
pressure air. Control signals are generated by the controller 300 to raise
or lower the electrically operated spindles 81 and 85 and to appropriately
position the X- Y table 70.
The controller 300 receives sensor signals from the tool magazine up and
down sensors 236 and 238, and from the sensors associated with the gripper
apparatus 100. These sensors include the up and down location sensors 106
and 108, and the tool shank position sensor comprising the light source
114 and detector 116. The controller 300 also receives spindle Z-axis
position information from the spindles 81 and 85, in the same manner as
described in U.S. Pat. No. 4,761,876.
The tool changer system may be operated to insert a tool in the chuck of
the particular drilling spindle, or to remove a tool from the spindle.
When inserting a tool into the spindle chuck, the optical sensor
comprising elements 114 and 116 may be employed in an insertion sequence
to position the tool shank in the chuck so that the tool drilling end
extends from the chuck a predetermined distance. The insertion and change
tool sequences are outlined below. In these sequence, it will be
understood that the magazine 200 is normally in the up position, the
gripper 100 is normally in the down position with the grip jaws open, and
the spindle are normally in the up position.
LARGE SPINDLES (85-88)
A. Insert Tool Sequence
1.Move the gripper 100 over under the selected tool in magazine.
2. Bring magazine down (to the tool change position), and move the gripper
up.
3. Close the gripper jaws to grab the drill with the high gripping
pressure.
4. Bring the magazine up and move the gripper down.
5. Move the X-Y table to position the gripper under the spindle.
6. Open the spindle chuck.
7. Raise the gripper to insert drill into the spindle chuck.
8. Close the chuck.
9. Reduce the gripper pressure to about 2 lb. holding force.
10. Lower the spindle until the optical sensor (114, 116) is triggered.
11. Increase the grip pressure.
12. Open the chuck.
13. Move the spindle down until the chuck contacts the gripper jaws.
14. Close the chuck.
15. Open the gripper.
16. Move the spindle up and the gripper down.
17. Ready to drill.
B. Change Tool Sequence
1. Move the gripper under the spindle.
2. Raise the gripper.
3. Close the gripper jaws to grab the drill.
4. Open the chuck.
5. Move the gripper down.
6. Move the gripper over under the selected clip opening in the magazine.
7. Lower the magazine and move the gripper up to insert the drill into the
clip opening.
8. Raise the magazine and lower the gripper.
9. Repeat the "Insert Tool Sequence" until finishing the drilling sequence.
SMALL SPINDLES (81-84)
A. Insert Tool Sequence
1. Move the gripper under the selected tool held in the magazine.
2. Lower the magazine to the tool change position.
3. Close the gripper to grab the drill.
4. Raise the magazine and move the gripper down.
5. Move the gripper under the spindle.
6. Raise the gripper to insert the drill into spindle.
7. Reduce the gripper pressure to about 1 lb. holding force.
8. Lower the spindle until the optic sensor is triggered.
9. Close the gripper.
10. Lower the spindle until the spindle contacts the gripper jaw tips.
11. Open the gripper.
12. Move the spindle up and the gripper down.
B. Change Tool Sequence
1. Move the gripper under the spindle.
2. Raise the gripper.
3. Close the gripper jaws to grab the drill.
4. Lower the gripper.
5. Move the gripper under the selected clip opening in the magazine.
6. Lower the magazine and raise the gripper to insert the drill into
magazine.
7. Open the gripper.
8. Raise the magazine and lower the gripper.
9. Repeat "Insert Tool Sequence."
The insertion sequence for inserting the tool with a predetermined length
extending from the spindle chuck is shown in FIGS. 16-27. Thus, the
gripper jaws are open (FIG. 16) as the gripper apparatus is raised and the
magazine lowered, and the tool 280 is gripped "short" (FIG. 17) by the
jaws 110, 112, i.e., the jaws are not brought up against the clip
structure, but grip the tool with a length of the shank between the tip of
the jaws and the bottom of the clip structure. The gripper apparatus is
lowered and the magazine raised to remove the tool from the clip (FIG.
18).
The gripper apparatus 100 carrying the tool 280 is then positioned under
the spindle chuck with the chuck jaws open in the case of the pneumatic
chuck (FIG. 19). The gripper apparatus is then raised (FIG. 20) to insert
the tool shank into the chuck jaws. The chuck jaws are then closed on the
tool shank (FIG. 21).
The following sequence results in the proper extension of the tool from the
chuck. The air pressure applied to the pneumatic actuator closing the
gripper jaws 110, 112 is substantially reduced to provide only a small
grip pressure on the tool shank, e.g., two pounds holding force. The
spindle is then lowered with the tool shank firmly gripped in the chuck,
so that the shank in the gripper jaws 110, 112, slides, until the end of
the tool triggers the optical sensor (114, 116) at phantom line 117 (FIG.
22). Full grip pressure is then applied to the gripper jaws, the jaws of
the spindle chuck are released, and the spindle lowered further until
about 0.040 inches in separation between the chuck and tips of the jaws
110, 112. At this point, the length of the tool extending from the chuck
has been registered, and the gripper jaws are opened (FIG. 23).
At FIG. 24 the spindle is raised and the gripper apparatus lowered. The
insertion sequence is now completed.
A further feature of the gripper apparatus 100 is illustrated in FIG. 25.
As shown therein, the gripper jaws 110 and 112 are formed with a relieved
area below the tips of the jaws to form an opening 115 between the jaws
when in the closed position. The opening allows the jaws to be used to
grip tightly the shank of a tool 282 having an oversized bit end, i.e., a
tool wherein the diameter of the drill operating end is larger than the
shank end.
It is understood that the above-described embodiments are merely
illustrative of the possible specific embodiments which may represent
principles of the present invention. Other arrangements may readily be
devised in accordance with these principles by those skilled in the art
without departing from the scope of the invention.
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